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clocksource: hyper-v: unexport __init-annotated hv_init_clocksource()

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[ Upstream commit 245b993d8f ]

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

  - Remove __init
  - Remove EXPORT_SYMBOL

I chose the latter for this case because the only in-tree call-site,
arch/x86/kernel/cpu/mshyperv.c is never compiled as modular.
(CONFIG_HYPERVISOR_GUEST is boolean)

Fixes: dd2cb34861 ("clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220606050238.4162200-1-masahiroy@kernel.org
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Masahiro Yamada 2022-06-06 14:02:38 +09:00 committed by Greg Kroah-Hartman
parent 11c870c0b5
commit cff3a7ce6e
1 changed files with 0 additions and 1 deletions
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1
drivers/clocksource/hyperv_timer.c
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@ -325,4 +325,3 @@ void __init hv_init_clocksource(void)
hv_sched_clock_offset = hyperv_cs->read(hyperv_cs); hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
hv_setup_sched_clock(read_hv_sched_clock_msr); hv_setup_sched_clock(read_hv_sched_clock_msr);
} }
EXPORT_SYMBOL_GPL(hv_init_clocksource);